Question: Let $a$ and $b$ be real numbers.  One of the roots of $x^3 + ax + b = 0$ is $1 + i \sqrt{3}.$  Find $a + b.$
Answer: Since the coefficients are real, another root is $1 - i \sqrt{3}.$  By Vieta's formulas, the sum of the roots is 0, so the third root is $-2.$  Hence, the cubic polynomial is
\begin{align*}
(x - 1 - i \sqrt{3})(x - 1 + i \sqrt{3})(x + 2) &= ((x - 1)^2 - (i \sqrt{3})^2)(x + 2) \\
&= ((x - 1)^2 + 3)(x + 2) \\
&= x^3 + 8.
\end{align*}Thus, $a = 0$ and $b = 8,$ so $a + b = \boxed{8}.$